1. Field of the Invention
The present invention relates to a method of manufacturing sinter forged aluminum parts with high strength that are suitable as various kinds of members for structure use and base material for plastic-working use. More particularly, the invention concerns a method of manufacturing sinter forged aluminum parts with high strength that are improved in elongation as well as in tensile strength.
2. Related Art
Regarding the aluminum sintered parts manufactured with the use of a powder-metallurgical method, there has been an increasing demand in recent years, since they are not only light in weight but also possible to possess preferable properties that cannot be obtained with cast materials, such as strength, wear resistance and the like. As the conventional aluminum sintered alloys, Al—Si—Cu-based alloys have been predominant, and they have been applied to the structural materials and wear-resistant materials. However, since the Al—Si—Cu-based sintered alloys are to an extent of 300 MPa or so in terms of the strength even when they are subjected to forging and heat treatment, the application of them is limited and sintered aluminum materials with a higher level of strength has been therefore expected to be produced.
Under the above-described circumstances, in regard to the sintered aluminum materials with a further high level of strength, Japanese Patent Application National Publication (Laid-Open) No. 11-504388 (PCT Application of International Publication No. WO96/34991) proposes a process for manufacturing, with the powder-metallurgical method, an aluminum alloy of 7000 series in International Designation System by aluminum Association, that is known as extra super duralumin, and describes in its Examples that aluminum alloy exhibits a tensile strength of 305 to 444 MPa and an elongation of 0.6 to 5.6%. However, according to the above process, if the aluminum alloy has a tensile strength exceeding 400 MPa, its elongation is 1.1% or less, and, if the aluminum alloy has an elongation of 5% or more on the contrary, its tensile strength is around 300 MPa. In short, it is not such a material that exhibits a high level of property in terms of both of the tensile strength and the elongation.
In recent years, a great demand for making the products lighter in weight has existed in the field of automobile parts, terminal machines for use as electronic materials, precision machine parts or the like. If there is provided a sintered aluminum alloy that has a strength that is equivalent to general steel products, the range of use as well as the purpose of use is possibly made wide.